To meet the demand for wireless data traffic having increased since deployment of 4G (4th-Generation) communication systems, efforts have been made to develop an improved 5G (5th-Generation) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
Device to device (D2D) communication is being studied in communication standard groups to enable data communication services between user equipments (UEs). During the D2D communication, a transmitting D2D UE can transmit data packets to a group of D2D UEs, broadcast data packets to all the D2D UEs, or send unicast data packets to a specific D2D UE. D2D communication between the transmitter and receiver(s) is connectionless in nature, i.e., there is no connection setup (e.g., no control messages are exchanged) between the transmitter and receiver before the transmitter starts transmitting the data packets. During the transmission, the transmitter includes a source identification (ID) and destination ID in the data packets. The source ID is set to the UE ID of the transmitter. The destination ID is the intended recipient of the transmitted packet. The destination ID indicates whether the packet is a broadcast packet or a unicast packet or a packet intended for a group.
FIG. 1 is a schematic diagram illustrating a protocol stack for D2D communication according to the related art.
Referring to FIG. 1, the packet data convergence protocol (PDCP) layer in the transmitter receives the data packets, i.e., Internet protocol (IP) packets or address resolution protocol (ARP) packets (PDCP service data units (SDUs)) from an upper layer. It secures the packet and also compresses the IP headers of IP packets. The processed packet PDCP protocol data unit (PDU) is sent to radio link control (RLC) layer. The RLC layer receives the PDCP PDUs (RLC SDUs) from the PDCP layer. It fragments the PDCP PDUs if needed and sends the RLC PDUs to a media access control (MAC) layer. The MAC layer multiplexes the RLC PDUs (or MAC SDUs) and sends the MAC PDU to a physical (PHY) layer for transmission on a PC5 interface (e.g., a wireless channel).
FIG. 2 is a schematic diagram illustrating a PDCP PDU for D2D communication according to the related art.
Referring to FIG. 2, the PDCP layer adds a PDCP header to each PDCP SDU. The PDCP header comprises of PDU type, pro-se group key (PGK) ID, pro-se traffic key (PTK) ID and PDCP sequence number (SN). The PDU type indicates whether the data in PDCP PDU is an ARP packet or an IP packet. In order to support the security a PGK is defined. PGK is specific to a group of D2D UEs. Multiple PGKs per group can be pre-provisioned in a UE. Each of these PGKs for the same group is identified using an 8 bit PGK ID. If a UE wants to send data packets to a group, then it derives a PTK from the PGK corresponding to that group. The PTK is identified using PTK ID. PTK is a group member specific key generated from the PGK. Each PTK is also associated with a 16 bit counter (or PDCP SN). The counter (or PDCP SN) is updated for every packet transmitted.
The transmitter always adds the PDCP header with the PDU type, PGK ID, PTK ID and PDCP SN in every PDCP PDU. The receiver always parses these four fields in every PDCP PDU. The transmitter and receiver always encrypt/decrypt the data in PDCP PDUs respectively.
In some D2D communication systems, whether or not to apply the security (e.g., encryption and/or integrity protection) can be configurable. In the case that the transmitter does not apply security, then the related art approach does not work as the receiver always assumes that data is encrypted in every PDCP PDU and using the PDCP security information in the PDCP header, the receiver derives the security keys and decrypts the data.
In some D2D communication system, a UE can be in coverage of network and another UE can be in out of network coverage. UE in coverage of network can receive the security configuration information from the network, while out of coverage UE must rely on pre-configuration or may not apply security in the absence of security configuration information. In the case that the receiving UE is in coverage and always assumes that data is encrypted in every PDCP PDU then communication will fail as the receiver attempts to decrypt the PDU which is not encrypted.
Thus, there is a need for a method to generate the PDCP PDU depending on whether or not the security is applied. Further, it is required to reduce the overhead in the radio interface by avoiding transmitting redundant information, especially when security is not applied, then it is not required to send the security information in the PDCP header.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.